1. Field of the Invention
The present invention relates to a water-in-oil emulsion composition for forming a silicone elastomer porous material, and more specifically to a water-in-oil emulsion composition which can produce a silicone elastomer porous material without being accompanied by a foaming phenomenon.
2. Description of the Related Art
Silicone elastomer porous materials are used in a variety of fields, for example, as parts of image forming devices such as photocopiers and laser printers, including developing rollers, toner feeding rollers, transfer rollers and drum cleaning rollers, as sheet feeding rollers of photocopiers, various types of printers and plotters, and as pressure rollers of fixing devices.
Conventionally, porous materials are produced mainly by utilizing foaming phenomenon. For foaming, a chemical foaming agent, a gas or water has been used as a foaming agent. The manufacture of silicone elastomer porous materials is not exception, and in most cases, silicone elastomer porous materials have been prepared by using one of these foaming agents. However, in such a conventional method of producing a silicone elastomer porous material, curing of silicone rubber and foaming are effected at simultaneously, with the result that cells (pores) in the resultant porous material are not uniform in size and their sizes vary in a wide range. Further, it is conventionally difficult to form cells having a size as small as, for example, 20 μm or less.
On the other hand, Jpn. Pat. Appln. KOKAI Publication No. 6-287348 discloses a method of producing a silicone elastomer porous material by freezing a room-temperature curing polysiloxane emulsion containing a polysiloxane having a silanol group, a specific crosslinking agent, a curing catalyst, and an emulsifying agent by refrigeration and sublimating the water to dry the frozen emulsion without defrosting it. Even with this method, it is still difficult to produce a porous material having uniform and fine cells. Further, the porous material obtained by this method is of an open cell type.